Overhead projectors of the transmissive type include a base unit which encloses a light source and lenses for suitably focussing light from the source and a transparent stage upon which may be positioned a transparency or other film having indicia which is to be projected on a distant screen. Above the base is disposed a projection head having lenses and a mirror which function to gather light from the projector base and redirect it to the screen. The projection head is supported by a post or arm extending upwardly from the base.
In typical prior art overhead projectors, as shown in FIG. 1, the primary structural member of the projection head assembly, the head bracket, is attached directly to the arm in a cantilevered fashion by screws positioned near the rear edge of the head bracket. The head bracket supports the projection lens and the mirror, as well as a head cover.
The technical problem addressed by this invention is the occurrence of undesirable vibration in the head of an overhead projector, such as when the projector is used with a liquid crystal display (LCD) panel. A LCD panel is used to allow projection of a computer generated image with an overhead projector. With some overhead projectors the cooling fan of the LCD panel causes an unacceptable resonant vibration of the projection head of the overhead projector. This vibration of the head, and particularly the mirror in the head, causes unacceptable smearing or blurring of the projected image.